Rechargeable batteries include valves that open and reduce the internal pressure of a case when the internal pressure of the case exceeds a predetermined pressure. When the valves open, gas is discharged out of the case. This reduces the internal pressure of the case.
Patent document 1 describes a battery module that includes a battery cell having a vent, which serves as a discharge passage for gas generated in the battery cell. The upper portion of the vent includes a degassing cover. The degassing cover, which is adhered and fixed to the upper portion of the vent, includes a degassing cover portion, a first extension, a second extension, and two first partition walls that extend between the first extension and the second extension. The first extension, the second extension, and the two first partition walls extend from one surface of the degassing cover portion toward a vent region of the battery cell. In the upper portion of the battery cell, the degassing cover portion, the first extension, the second extension, and the two first partition walls define a passage, through which gas is discharged.